Boiler feeding pump and method of operating the same



Aug. 15, 1939 I R. HINGST 2,169,418

BOILER FEEDING PUMP AND METHOD OF OPERATING THE SAME Filed July 15, 19363 Sheets-Sheet 1 Aug. 15, 1939 R. HINGST 2,169,418

BOILER FEEDING PUMP AND METHOD OF OPERATING THE SAME Filed July 15, 1936'3 sheets-sheet 2 Aug. 15, 1939 R. HINGST 2,169,413

ND METHOD OF OPERATING THE SAME BOILER FEEDING PUMP A Filed July 15,1936 s Sheets-Sheet 5 Patented Aug. 15, 1939 UNITED STATES PATENT OFFICERudolf Hingst, BerIin-T'egel, Germany, assignor to Rheinmetall-BorsiBerlin-T'egel, Germany,

g Aktiengesellschaft,

a corporation Application July 15, 1936, Serial No. 90,769 In GermanyJuly 1'7, 1935 13 Claims.

Centrifugal pumps are widely employed today for boiler feeding systems.However, these pumps have distinct disadvantages which very often affectan economic operation of such feeding systems.

The height of lift (head) of centrifugal pumps is determined by thecentrifugal action of the impeller and by the transformation of theenergy of the velocity of efllux into pressure energy within theimpeller. To those skilled in the art it is known that considerablelosses occur in centrifugal pumps through leakage, skin friction betweenthe impeller and fluid, and unsatisfactory transformation of velocityenergy into pressure. These losses in centrifugal pumps maybe keptwithin tolerable limits when the pump is constructed for a largedelivery and a small height of lift (head). If the height of lift,however, is to be large, the above mentioned losses in centrifugal pumpsmay only be reduced by resorting to multi-stage construction of suchtypes of pumps. The efiiciency of multi-stage centrifugal pumps forgreat heights of lift and a small delivery is so low that the operationof the same is not sufiiciently economical for practical purposes.

In the present invention these disadvantages have been eliminated byarranging the impeller within a housing and subjecting the same to steampressure, and by transforming the pressure of the lifted fluid intotangential velocity by means of jets arranged on the impeller. Toaccomplish the above the impeller consists of a hollow member providedwith a plurality of jets at its circumference for the discharge of fluidlifted by its centrifugal action. The jets are arranged in a directionopposite the rotation of the impeller so that by reaction action of thedischarging fluid a portion of the energy utilized for placing the fluidunder pressure may be reclaimed.

The present invention further relates to centrifugal boiler feed pumpsystems wherein superfiuous feed water, which has entered the boiler,may be discharged therefrom and utilized for controlling the admissionof fresh feed water to the boiler, thereby affecting the operation ofthe pump.

The present invention further relates to centrifugal boiler feed systemsfor so-called forced circulation boilers, and includes arrangements forreturning the water content of a steam-water mixture from a single pipeevaporator, to the boiler.

Further and other advantages of the present invention will becomeapparent from the following description and drawings, in which Figure 1illustrates a centrifugal feed Water pump arrangement for boilers,wherein the impeller is arranged within a housing and within which it issubjected to the steam pressure of a boiler in conjunction with which itis to be used.

Figure 2 shows an arrangement wherein the impeller of the centrifugalpump is located directly within the steam compartment of a boiler.

Figure 3 shows a centrifugal feed water pump arrangement of the type ofthe present invention, wherein the amount of delivery can be variedwithout variation of the revolutions of the pump.

Figure 4 shows an arrangement of the present invention in connectionwith a forced circulation boiler.

Figure 5 shows a construction similar to that of Figure 4, wherein theimpellers are arranged on one shaft and in substantially the samehorizontal plane.

Referring first to Figure 1, I indicates the impeller of the centrifugalpump which is of a construction to form a completely closed compartmentprovided at its circumference with a plurality of jets 4 which arearranged on the impeller in such a manner as to discharge fluidtherefrom in a direction opposite to the direction of rotation of theimpeller. The impeller I is mounted upon a shaft 2 which is hollow andutilized for the admission of fluid into the impeller compartment.Mounted on shaft 2 is also another impeller 9, which is of commercialconstruction. A housing 6 encloses the shaft 2 and the impellers I and 9in a manner clearly shown in Figure l, and is provided with pipe lines Iand III for connecting the housing 6 with a boiler, in conjunction withwhich this centrifugal pump is to be used. The pipe line 1 is connectedto the steam compartment of the boiler, and the impeller I withinthecompartment 6 is thereby subjected to exactly the same steam pressure asexists in the boiler..

In operating the pump described herein, the impeller I must be rotatedat a speed so as to lift the fluid through the hollow shaft 2 into thecompartment of the impeller I and to discharge the same therefromthrough the orifice or jets 4 against the pressure within thecompartment 6. The fluid or feed water enters the compartment 6 andflows toward impeller 9 which forcesthe same through the pipe line I 0of the housing 6 or a line connected with the same, into the boiler.

It should therefore be noted that the impeller I of the centrifugal pumpis adapted to bring the feed water to the required pressure while theimpeller 9 forces the water into the boiler, and need only overcome theresistance of the pipe line, which is connected with the pipe line Ill.

The pum construction as illustrated in Figure i will not have the usualleakage loss of these types of centrifugal pumps, and the skin frictionof the impeller is very considerably reduced because the same runs insteam and not in water. The jets 4 transform the pressure intotangential. velocity, and, by arranging these jets so-as to dischargethe water in a direction opposite the direction of rotation of energy ofthe water is reclaimed'by a reaction action upon the impeller I. Theamount of water discharged from the jets 4 is dependent upon thepressure difference between the water pressure at the circumference ofthe impeller. I. and the steam pressure within the compartment 6.-Regulation of the quantity of water to be handled by the pump during aconstant steam pressure in the boiler can therefore be effected bychanging the water pressure, which is accomplished by varying the speedof rotation of the impeller upon which the water pressure is de--pendent. r r

The efliciency of placing the water under pres sure in the closedpropeller structure, and the reclaiming of a part of the used energy byreaction of the water discharging from the jets may be stated asfolloWs:--

wherein w is'the tangential velocity (discharge velocity) of the waterdischarged from the jets 4, and u the speed of rotation of the impellerI. The efliciency increases with increasing tangential velocity(discharge velocity) iv from'0.5 to a maximum. In view of the fact thatthetangential or discharge velocity depends upon the pressure differencebetween the water and the steam pressure, the efiiciency of the pumpwill be increased at higher pressure differences. The impeller I maytherefore be preferably constructed for a considerably higher pressurethan the boiler pressure.

Figure 2 shows a modification of the present invention. It will be notedfrom Figure 2 that the boiler 8 is provided with a dome-shapedcompartment 8 within which the impeller II is e the same and theimpeller I I.'

arranged. In this form of construction a separate housing for theimpeller is not necessary. The impeller I I' is mounted on hollow shaft2 rotati vely' arranged within the compartment 8, while a motor or otherprime mover outside of the compartment 8', or turbine I2 within thecompartment'fl', may be'utilized for imparting rotative movement to theimpeller I I. The turbine should be arranged within the compartment '8'of the boilerin' such a manner that all steam passing from the boilermust pass said; turbine to thereby operate the same. 'The' turbine wheelis mourited directl'y'upon thehollow shaft 2, and in this way therotation is directly imparted to 7 The feed Water is delivered to thepump from a storage tank which is placed at a higher elevation than: thecompartment 8, or another pump maybe usedfor'delivering thewater to theimpeller I I. In the arfra'ng ement'shown in Figure 2, feed water willbe discharged into the boiler as soon as the speed of rotation of theimpeller is sufficient to sub- .ject thefeed water to a pressureslightlyhigher I'2'which operates the impeller II,

the impeller" I, discharge 7 than the pressure within the boiler. Theregulation of the delivery of this kind of pump can be effectedbyrchanging the speed of the prime mover which operates the pump. Incase a turbine is used for the operation of the impeller wheel, anautomatic regulation of the water supply in connection with the steamconsumption may be attained because all the steam pro duced inthe boiler8 will pass through the turbine and in this way... the addition of freshwater may be accomplished, which is of course in a certain ratio to= thesteam produced, and discharged from the boiler.

In the types of centrifugal pumps referred to above, a regulation of thedelivery of the pump in accordance with the steam consumption can onlybe effected by variation of the number of revolutions of the prime moverwhich operates the pump. -In Figure 3, therefore, there is shown anarrangement of boiler feed pump which permits a regulation of thedelivery thereof without variation of the speed of operation of thesame. In this construction the impeller I is mounted within the steamcompartment of the boiler 8 similar to the arrangement of Figure 2.However, in this case the impeller* itself is divided into two chambersII and I6, the chamber or compartment I6 of the impeller I being incommunication with a compartment I6 into which superfluous feed waterfrom the boiler 8 is dis-i charged by means of a pump I5 connected tosaid compartment I6 by means ofa pipe line I5. Arranged within theboiler 81is an overflow I8 connected with the pump I5 by means of a pipeline I8. The impeller I is mounted on the hollow shaft 2, the latterbeing rotatably mounted 6 within the compartment I6;

Water is supplied to the impeller I from a reservoir and brought underpressureby the centrifugal action within the compartment II of theimpeller I slightly above the pressure. of the boiler, whereupon'thewater will be discharged into the boiler. Should suflicient water besupplied to boiler 8 and the water rise over the required level, it willbe discharged into the member I8, pipe line I8, and pump I5. The pump I5delivers the water through the line "I5' into compartment I6 from whereit enters the upper compartment I6 of the impeller I.

From the above it will be seen that for the normal feeding operation ofthe pump the'compartment II of the impeller I in Figure 3 is utilized.The compartment II, communication with the compartment I6 on theperiphery of the impeller. As in the compartment I6 of the impeller Ionly a pressure in-' crease from the boiler pressure to the pressure atthe periphery of the impeller I is necessary; another pressure increaseon the periphery of the impeller will occur as soon as has been fed intothe b oiler and "has been returned byp ump I5 to-chambersf I6 and I6 ofthe impeller I, and at this time, when the limit of the maximumefiiciency of the centrifugal however, is in toov much water I in Figure4, wherein a feed system is disclosed for feeding water into a forcedcirculation boiler 25.

ure 3, the only difference being that the produced steam-water mixtureis forcibly returned to the compartment I6 of the impeller I through thepipe line I9. The moisture contained in the steam is separated bycentrifugal action, and the saturated steam is supplied through a pipeline 26 to a super-heater 22. The water discharged by the impeller I inFigure 4 flows to a pump 23 which is mounted on the shaft 2, which alsocarries the impeller I, and is forced from the same to the evaporator 25of the forced circulation boiler.

Figure 5 shows substantially the same arrangement as seen in Figure 4,and corresponding parts have been correspondingly indicated. However,the impeller of the pump 23 is mounted on a shaft 2', as is the impellerI, and is also arranged in substantially the same horizontal plane asthe impeller I, In other words, the impeller 23' of pump 23 surroundsthe impeller I at its circumference. In this construction the impeller23' of pump 23 is rotated at a lower speed than the impeller I, and bothimpellers are driven preferably by the some source of energy.Transmission means 26 are mounted between the shaft 2 which carries theimpeller I, and shaft 2' which carries the impeller 23' of pump 23, forproducing the desired speed reduction. The direction of rotation of theimpellers I and 23' may be preferably the same, and both impellers I and23 may be operated, if desired, by a back flow turbine.

Having thus described my invention, what I claim as new and desire tosecure by Letters Patent of the United States, is

1. A device for supplying feed water to a. boiler, comprising, incombination, a housing, means for admitting steam from said boiler intothe housing, a hollow rotatable impeller structure within upon rotationof the latter, and instrumentalities for rotating the impeller structurewithin the housing for lifting feed water into the impeller structurefor subjecting the feed water to a pressure exceeding the steam pressureand for expelling the same into the boiler under transformation of suchpressure into velocity of efllux.

2. A device of the class described for supplying feed water to a boilerunder steam pressure, comprising, in combination, a closed hollowimpeller structure having feed water inlet and outlet means, means forsubmerging the hollow impeller within the steam pressure of the boilerin such manner that the impeller is not submerged in the water in theboiler, and instrumentalities for operating said impeller structure forcausing delivery of feed water thereto and expulsion thereof into theboiler at a pressure exceeding the steam pressure of the boiler.

3. A device of the class described for supplying feed water to a boilerunder steam pressure, comprising, in combination, a closed hollowimpeller structure having feed water inlet and outlet means, a source offeed water in communication with the inlet means of the hollow impellerstructure, means for submerging the hollow impeller within the steampressure of the boiler but exeluding steam from the impeller, andinstrumentalites for operating said impeller structure for causingdelivery of feed water thereto and expulsion thereof into the boiler ata pressure exceeding the steam pressure of the boiler.

4. A device of the character described, comprising, in combination, ahousing, a shaft Within said housing, a closed hollow impeller structureon said shaft and rotatable within said housing, saidimpeller structurebeing provided with a fluid inlet opening and a plurality of fluidoutlet openings, means for connecting said housing with the steamcompartment of a boiler, and means for connecting the fluid inlet ofsaid impeller with a source of feed water supply so that only feed watercan enter said impeller.

5. A device of the character described, comprising, in combination, ahousing, a hollow shaft within said housing, a closed hollow impellerstructure on said shaft and rotatable within said housing, forming animpeller compartment in communication with the hollow shaft, a pluralityof discharge jets on said impeller structure, means for establishingcommunication between said housing and the steam compartment of aboiler, and means for establishing communication between said impellercompartment and a source of feed water supply through said hollow shaftaforesaid so that only feed water can enter said impeller.

6. A device of the character described, comprising, in combination, ahousing, a shaft, a closed hollow impeller structure on said shaft androtatable within said housing, the impeller structure being providedwith fluid inlet means at a point of relatively low circumferentialspeed, a plurality of jets on said impeller structure at points ofrelatively high circumferential speed for discharging fluid therefrom,means for establishthe steam compartconnecting the fluid inlet means ofsaid impeller with a source of feed water supply so that only feed watercan enter said impeller.

7. A device of the character described, comprising, in combination, ahousing, a shaft, a closed hollow impeller structure on said shaft androtatable within said housing, the impeller structure being providedwith fluid inlet means, a plurality of jets on said impeller structurearranged so as to discharge fluid therefrom in a direction opposite tothe rotation of said impeller structure, means for establishingcommunication between the steam compartment of a boiler and saidhousing, and means for connecting the fluid inlet of said impeller witha source of feed water sup ply so that only feed water can enter saidimpeller.

8. Apparatus as defined in claim 6, in combination with a secondcentrifugal pump including a rotary impeller arranged to receive thefeed water discharged from the jets of the first impeller, and means forconnecting the second pump with the boiler so as to direct the feedwater thereto.

9. Apparatus as defined in claim 6, in combination with a secondcentrifugal pump including a rotary impeller arranged coaxially in thehousing and disposed in the same plane as the first impeller to receivethe feed Water discharged from the jets of the first impeller, and meansfor connecting the second pump with the boiler so as to direct the feedwater thereto.

10. Apparatus as defined in claim 6, in combination with a secondcentrifugal pump including a rotary vane impeller arranged to receivethe ieed water discharged from the jets of the first impeller, and meansfor connecting the second pump with the boiler so as to direct the feedwater thereto. 7 v

11; Apparatus as defined in claim 6, in combination with a secondcentrifugal pump including a rotary impeller arranged to receive thefeed water discharged from the jets of the first impeller, means forconnecting the second pump with the boiler so as to direct the feedwater thereto, and means for driving said second impeller at a slowerspeed than the first impeller.

12. A centrifugal pump for supplying feed water to a boiler having asteam compartment comprising, in :combination, a housing adapted tocommunicate with the boiler steam compartment, a shaft within saidhousing, and a closed hollow impeller structure carried by said shaftand rotatably mounted within said housing comprising a plurality ofcompartments having restricted outlet jets at their periphery and havingrelatively unrestricted intercommun'i'cation, at least one of whichcompartments is adapted to communioate with a source of feed watersupply and the other compartment with a pressure medium for varying thepressure at the impeller jets aforesaid to effect a control of thedelivery of the Pump.

13. A feed water system for boilers or the like, comprising, incombination, a housing adapted to communicate with the steam space ofthe boiler, a shaft within said housing, a closed hollow impellerstructure carried by said shaft and rotatably mounted within saidhousing comprising a plurality of compartments adapted to communicatewith a source of feed water supply, said impeller structure having aplurality of restricted outlet jets at its periphery for discharging thewater into the housing at a pressure greater than the steam pressuretherein, and said compartments having relatively unrestrictedintercommunioation, and means for returning superfluous feed water fromthe boiler to at least one of said impeller compartments for controllingthe feeding operation of the impeller responsive to the additionalpressure created by the superfluous feed water within the impellerstructure at the outlet jets.

RUDOLF HINGST.

